This section provides background information related to the present disclosure which is not necessarily prior art.
Fire protection sprinklers are designed and widely used for commercial and residential applications to control or suppress a fire. In commercial applications there are environmental conditions that can dictate which types of sprinklers are utilized in the commercial environment. The commercial application can include a hazard type or commodity that is being stored in the commercial environment, the ceiling height, the height of storage that can be stacked on racks, the presence of obstructions, the coverage area needed to be protected, the spacing between the sprinkler heads and the available water supply. For residential applications, the coverage area, spacing, water supply, ceiling type, as well as other aesthetic concerns may apply. The National Fire Protection Association (NFPA) provides standards that define the minimum requirements for the designing and installation of automatic fire sprinkler systems. One type of fire protection system is a fire suppression system in which the sprinkler system is designed to sharply reduce the heat release rate of a fire and prevent its re-growth by means of direct and sufficient application of water or other fire suppressant through the fire plume to the burning fuel source. A fire control system is designed to limit the size of a fire by distribution of water so as to decrease the heat release rate and pre-wet adjacent combustibles while controlling ceiling gas temperatures to avoid structural damage. The NFPA provides different standards for fire suppression and fire control.
Both Underwriters Laboratories (UL) and Factory Mutual Approvals (FM) provide fire testing of sprinkler designs for meeting their intended design purpose. For successful fire suppression or control tests performed at UL or FM, the tests provide baseline data for water distribution and response time requirements for future designs intended to meet the same design requirements. The baselines are used to establish water distribution requirements for testing of the future sprinklers and these baseline water distribution requirements are determined based upon water distribution tests of the sprinkler heads that were tested to successfully control or suppress a fire as required. The sprinkler characteristics that are important for meeting design requirements typically include the required delivered density (RDD), the actual delivered density (ADD), the thermal sensitivity of the sprinkler, and the operating time of the sprinkler. In general, if a subsequently designed sprinkler has the same or improved water distribution in order to meet the required delivered density and actual delivered density requirements, and the sprinkler's thermal sensitivity and operating time are within the required limits, the sprinkler design can be approved without the necessity for conducting further actual fire tests which can be very expensive and time consuming.
Each different sprinkler type demands a different type of water spray pattern to achieve either fire control or suppression. Standard coverage ordinary hazard sprinklers generally protect a maximum coverage area of 130 square feet. According to the guidelines of the NFPA, extended coverage ordinary hazard sprinklers must protect from 225 to 400 square feet. Several factors can influence the water distribution patterns of a sprinkler. The different spray patterns achieved by different sprinkler types are provided by varying such factors as the shape of the sprinkler frame, the K-factor, and the geometry of the deflector position below the frame for creating a spray pattern. For applications where more water is required for control or suppression, the K factor is increased to meet the demand for additional water. In addition, the water supply pressure may also be increased or decreased to meet the demands.
The deflector geometry is particularly significant since the deflector is the main component of the sprinkler assembly and to a great extent, defines the size, shape, uniformity, and water droplet size of the pattern. Often times, a new sprinkler design can be achieved by utilizing an existing deflector geometry and/or by making minor modifications to the lengths or widths of the slots provided in the deflector. However, with some sprinkler designs, a simple modification of an existing deflector geometry does not adequately provide the water distribution pattern necessary for a desired application.